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Why don't bombers have close-in weapon systems (CIWS)?
Besides the TU-22 radar-controlled rear-cannon, why aren't there close-in weapon systems (CIWS) on planes to defend against incoming missiles? The tech seems to be there.

Other types of countermeasures have a better weight to effectiveness tradeoff.

Machine gun based missile defense only works when the missile has a pre defined trajectory. Even on ships if the missile choose to maneuver the machine gun is pretty much useless. On a plane you have both the gun platform and missile maneuvering fiercely. Also the latest bombers all rely on not being detected as the survival strategy so if a missile is on the way the battle is already lost.

a Phalanx CIWS weighs 6 tons, that would seriously reduce the payload of a bomber.

As mentioned, chaff, flares, IR and RF jamming, and stealth are more effective per kg than a gun-based CIWS. Additionally, lasers and small missiles designed to kill/disable incoming missiles are being developed: SHiELD (~30 kW laser) is scheduled to demo in 2021; MSDM (mini anti-missile missile) is expected to debut "soon."

The main reason is the same reason why CIWS are not used on ground vehicles - anything smaller than a ship just doesn't have enough space/weight allowance to fit one, let alone two. The lightest CIWS I found, an outdated version of Soviet AK-630 system, weighs in at 1 ton (later versions are much heavier), has a turret ring 1m across, is 1 meter high above deck and needs 2m of space below (which means that installing one would also going to be aerodynamically awkward) - and all of this does not include the ammo supply (2000 shells for this version translate to additional 0.2 tons, later versions, again, had more ammo). All modern CIWS weigh at least 6 tons, are considerably bigger, and some of them also need an external targeting radar - and I assume not all bombers have the equipment needed by default. Aircraft also has more approach vectors to cover - a ship only needs CIWS installed on top, but a bomber would also need defence in the lower hemisphere; so for complete coverage we would need even more guns, which would mean even less speed and payload.
Even if we would manage to fit some in - gun-type CIWS effectiveness is disputed. Their limited range means that even a succesfull kill on an incoming missile might not protect the ship from an impact - and what would be a minor inconvenience for a warship, will be a deathblow to an aircraft. Missile-based defences are usually considered a better choice, as they can engage and destroy incoming missiles at significant range from the protected object - but they are even heavier and bulkier than guns.
And last, but not least - modern strategic bombers tend to eschew defensive armaments at all, because their main weapons are missile-based, and imply a launch at safe distance from the enemy.
Thus - modern CIWS on a bomber are impractical. They are heavy, bulky and do not provide immunity to missiles, so might as well stay on the ground.
P.S. On a closer inspection, several other bombers had or have radar-controlled tail guns - Tu-95 or early B-52, for example. B-52's tail turrets were removed after a friendly-fire incident where radar-homing HARM missile locked onto the gun's targeting radar - another downside that I haven't noticed before.

The USN A3 (USAF B66) was a bomber.  It had a radar guided tail gun.  When repurposed as an ECM aircraft, the gun and radar were removed and replaced with jamming electronics.


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How do VOR beacons detect?
I assume that any military aircraft can find the position to any VOR ground station. Is the VOR invisible to the military aircraft?

https://en.wikipedia.org/wiki/Security_Control_of_Air_Traffic_and_Air_Navigation_Aids

VOR and Radar are different things.

Sorry for confusing the terms VOR and Radar, and to be more specific in my question, is the VOR station location visible to any aircraft that has a receiving unit? Can the VOR be hidden from aircraft?

A VOR is very easily found - provided you know the frequency (which will be published on charts, etc). Simply adjust your NAV radial until you are roughly on course, and fly in that direction for a while. If the VOR has a DME then you will know exactly when you are over it, otherwise you will just wait until your course offset swings rapidly

I don't think the last edit helped.  Now the two sentences of answer seem to contradict each other.  And title has become extremely broad.   Before the edit we sort of knew why you were asking the question, even though it arguably didn't seem to reflect much prior research effort.  Sorry, just my 2c, consider rolling back?

VOR is a civilian navigation aid. Unless turned off, any aircraft equipped with a receiver can receive the station's broadcast signal for a relative bearing. This includes military aircraft. A defending nation is of course able to turn their VOR stations off, should they find out that their adversary is so ill prepared that they have to rely on civilian navigation aids.

The position of each VOR station is published, since knowing you're at some range & bearing from XYZ is only useful when you know where XYZ is. So even with the VOR not transmitting, its location is still known to the world.

@Sanchises thanks for the explanations, though I did not understand the last sentence.

@RalphJ thanks for the further explanation! so if the VOR station is unpublished and turned-off then they won't be detected. Where are the VORs being published? Is there an international center for that?

@knowledgeloverx Every country has an "aeronautical aviation publication" (AIP) that is structured according to international conventions (i.e. Appendix 2 of ICAO-Doc-1006). You will typically find VORs in section "ENR 4.1 - radio navigation aids".

You can find the direction of a VOR transmitter. You can't find its position - range and direction - unless it's a VORTAC station and you have a TACAN interrogator. There are missiles like the HARM that target radar transmitters. They follow the signal to its source. I don't think VOR beacons are considered to be worth the expense.

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What callsign should an ultralight use?
I plan to operate an ultralight aircraft domestically (in Oregon, USA) in uncontrolled airspace and will not venture out of the country nor will I come near the Canadian or Mexican borders.
I have searched a bit and found that as long as I'm going to be operating domestically, I don't need an FCC license, however in AC 103-6 it states

c. Traffic Advisory Practices at Uncontrolled Airports.
In all radio communications, ultralight operators should state the word
  "ultralight" followed by the call letters assigned by the F.C.C. on your
  radio license, i.e., "Ultralight 12593U".

How can I use FCC call-letters if a license is not required domestically?  Since ultralights aren't required to be registered, I won't have a tail number to use either.  Do I just make something up like "ultralight whisky bravo" (my initials)? I do have an amateur radio license, but I'm guessing that isn't relevant here.

The "call-letters" are the FAA registration numbers for your aircraft, not your license.

@RonBeyer Thanks for that. I understand that either FCC call-letters or the tail number can be used, but since ultralights aren't required to be registered, it still leaves me wondering what to use in my situation.

One of the suggested communication strategies for uncontrolled airports is to announce the type of aircraft and color. e.g. “Brown and white Cherokee entering downwind”. Rather than using your initials, which like the tail number, don‘t really give any information, why not use your color or some distinguishing feature. e.g “Red tricycle ultralight” or “Blue weight-shift ultralight”. Anyone out there would have a better chance of knowing  what to look for and seeing and avoiding you.

@JScarry Thank you for that.  If you post that as an answer, I'll mark it as the best answer.  Thanks :-)

I edited your question a little: there is no 14 CFR 103.25, but I found the text you used in AC 103-6. I hope that's the correct source but if you found it elsewhere then you can edit your question to change it.

Not living in the US, but could the FCC license be related to the radio instead of the aircraft? If you have the right to transmit in the aviation band, it's surely because you have a radio license and a call sign...?

There are two types of FCC radio licenses pilots need to know about. One if for the operator (pilot), I have one from the 80s when they were required of all pilots. The other is for the radio station (aircraft). They are required for flights outside the country, but the rules are not enforced for Canada and Mexico. I don’t know about elsewhere.

@Pondlife Ah yes, sorry about the misidentification.  The document I was reading made it difficult to see where FAR 103 ended and AC 103-6 started.  Thanks!

You aren't required to get an FCC radio license for domestic flying, but you can get one. They're cheap, easy and good for life.

One of the suggested communication strategies for uncontrolled airports is to announce the type of aircraft and color. e.g. “Brown and white Cherokee entering downwind”.
Rather than using your initials, which like the tail number, don‘t really give any information, why not use your color or some distinguishing feature. e.g “Red tricycle ultralight” or “Blue weight-shift ultralight”.
Anyone out there would have a better chance of knowing what to look for and seeing and avoiding you.

According to AC 90-66C: “‘Self-announce’ is a procedure whereby pilots broadcast their aircraft call sign, position, altitude, and intended flight activity or ground operation on the designated CTAF. … Self-announcing should include aircraft type to aid in identification and detection, but should not use paint schemes or color descriptions to replace the use of the aircraft call sign.”

I fly a Part 103 Ultralight. I simply use "Ultralight" when announcing my position and intentions. If there are any other ultralights in the area, I will add the color for a more descriptive designator "Blue and White Ultralight". Also, if I am flying in a close group of other ultralights (50-100 yards apart or so), Only one of us will simply announce, for example "John Day Traffic, Flight of 3 Ultralights is turning left downwind, Runway 26, John Day". We sometimes land all at once, within seconds of each other (sometimes all of us on final at the same time), to keep from causing too much of a congestive situation at airports where there is a busy fly-in. For example, if there are 4 of us arriving at an airport, it is much more expeditious for us to group together on downwind, then turn one at a time on base seconds from each other, then final with maybe 1/8 mile spacing max (an ultralight wing makes hardly a ripple in the air, so turbulence from wing vortexes is not much of a factor at all 50 yards back), rather than have a bunch of slow moving ultralights hogging the whole pattern for the entire 10 to 15 minutes it would take for all of us to enter and stay in a typical 45 degree entry pattern with "normal" GA spacing. This way, any GA pilots in the area or pattern will simply have to look for a cluster of 4 slow moving aircraft grouped closely together to spot all of us at once.

According to the FAA, they told me that these days, your just to use the license number of your radio followed by Ultralight. So... rhp530 ultralight.
My radio is the Rexon rhp-530.

the FCC license required is for the radio itself.  Most two-way radios (even some kid's walkie-talkies) sold in the US require licenses, however few people/businesses ever actually get them.  here is a website that does a decent job describing the licensing issue, in my opinion:
https://nuradios.com/fcc-info/
so your call-sign would be your FCC (not FAA) radio license number followed by 'Ultralight'  however Hollywood call-signs, such as using air-frame primary colors, followed by "Ultralight" are often times accepted.  in my experience, as long as you are identifiable and safe, few complaints will be heard.

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From which rating would it be easier to transition to an Osprey? Fixed-wing or rotary-wing?
If the future of flight was to be on aircraft that were a hybrid of fixed-wing and rotary-wing (for example the Osprey), assuming they had similar technical abilities and the same number of flight hours, who would have an easier time flying an Osprey?
Or to put it another way, is the Osprey closer to a plane or to a helicopter?

The Osprey is closer to a helicopter and if I was going to chose from a fixed wing pilot or rotary pilot to train on it I'd choose the rotary pilot.  The rotary wing physical skill set is so much more demanding than the fixed wing one.  A helicopter pilot could master fixed wing cruising flight in the Osprey far easier than a fixed wing pilot could master hovering the Osprey (you can pretty much train a monkey to fly an airplane in cruising flight - airplane physical demands are mostly when you slow down).

The Marine Corps shares your opinion, drawing Osprey pilots from the ranks of helicopter trained aircrew.

I believe the FAA considers the Osprey or the AW-609 to be a powered lift category aircraft per §1.1.  Therefore if you were an Osprey pilot and you completed the conversion of your military pilot certificate and ratings, you would hold an FAA commercial certificate in the powered lift category and class with an instrument powered lift rating.  Given that your primary flight training (if you’re former USAF/USN) was in airplanes, they may add airplane single engine land as well with an instrument airplane rating too.
If the FAA’s policy stands, powered lift is a hybrid of airplane and rotorcraft helicopter aircraft but so different that the FAA considers it to be its own category and requires meeting the aeronautical experience requirements and passing a practical exam before being able to serve as PIC in such an aircraft.

Generally, in my opinion a vehicle like ospery is resembling an aircraft charateristic more than a helicopter.
From the flight physics perspective, ospery is behaving "completely" like an aircraft in most of its flight time (cruise phase), while at take-off and landing, the vehicle is operating in a "similar" manner to a helicopter. For example, most of helicopters use their tail rotor for providing directional contol, while ospery does not have any tail rotor. A helicopter uses its primary rotors for vertival, longitudinal and lateral movements, while ospery uses them only for  the vertical and longitudinal motions. For this reason, it seems different skills than flying a helicopter are required to be able to land an ospery.
Generally, I think the capability of landing or taking off vertically would not essentially make it a helicopter, as nobody considers the F-35B (the USMC version) as a helicopter. But, I acknowledge that the rotors may be misleading in the ospery case.

I don't know enough about osprey to give a reasoned answer, but helicopters have many configurations, and only 1 of those involves a tail rotor. [Assuming in hover mode it behaves similar to a Chinook.]

@wanna-beCanadianPilot Actually, I meant the small vetrically placed rotors at the end of the tail boom. This configuration seems to be most used one among the helicopters, while a minority have used other configurations such as tandem-rotor (such as CH-47 chinook) and coaxial rotors (such as Ka-52).


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Do Boeing and Airbus learn from each other?
Air France Flight 447 crashed into the Atlantic Ocean in June 2009. It was later revealed that the FO was unwittingly pulling the sidestick back, stalling the aircraft. The aircraft was an Airbus 330.
China Airlines Flight 006 almost crashed in February 1985 when the captain failed to step on the rudder after a sudden single engine failure at its cruising altitude and it got into a steep spiral. It recovered from the spiral descent thousands of feet above the Pacific Ocean but it experienced significant structural damages. The aircraft was a Boeing 747.
Some people say that the first accident could have been prevented if the sidesticks of the pilots had been inter-connected such that when one pilot moves his sidestick the other moves the same, just like the yoke system of Boeing aircraft. Also, some people say the second accident could have been prevented if the autopilot system had been programmed to correct excessive roll or pitch maneuvers caused by the pilot's control inputs or their absence.
But it looks like neither of the companies has adopted such suggestions, and that got me curious. Do they learn from each other? Do they correct their systems based on their competitor's accidents?

It's more the authorities learning from accidents and issuing new rules and regulations which affect both companies. Once a design is certified, the manufacturer always prefers to leave it unchanged. All aspects of a design had been thought over before several times and the one freak incident is unlikely to change the conclusion which had been reached earlier.

Is this question restricted to just the cockpit interface?  Parts of the question sound a lot more general than that.

Yes Airbus and Boeing learn from each other: they compete with each other. Both are implementing successful features of the competitor, and when the A320 came to market it required differentiating features to gain market share. The competing design from Boeing, the 737Classic, was completely re-designed in the 90s because of the lower specific fuel consumption of the A320. The other Boeing product competing in this class, the B757, is out of production. The resulting 737NG has outstanding fuel economy as well, partly achieved by the blended winglet which Boeing pioneered for this class of aircraft.

Where the two companies differ is in the design philosophy for interaction of the pilot with the aircraft. The A320 is actually the oldest design of Airbus that is still produced - the type was certified in 1988, while the 737 and the 747 type certificates were issued two decades earlier. The 737 MAX still has a common type rating with the original B737-100 and this poses a limit on the introduction of new flight crew ergonomics. The A320 could completely re-design all known features in cockpit control and implement new ones from military aircraft, such as the side stick which made the F-16 such a successful air superiority fighter.
The OP focuses on accidents and incidents which happened with the planes, due to incorrect pilot action. This is a subject where everybody learns from everybody, to continue to make air travel safer:

Every accident is thoroughly analysed in order to find the cause and prevent it from happening again in the future. This is done by independent government organisation who only focus on the cause of the accident, nothing else. The NTSB in the USA, the BEA in France.
As a result of this, there may be improvements imposed by the overseeing regulatory aviation organisations: FAA in the USA, EASA in Europe. They may write directives for aircraft manufacturers to implement changes in the design of the aircraft if that is where the incident cause was, or in the training procedures of pilots if pilot error was found to be a factor.

The ultimate proof of the pudding is in safety, and both Boeing and Airbus have excellent and very similar safety records for their aeroplanes. There are many ways that lead to Rome - everybody learns from everybody, and continues to improve their design which will always differ to an extent from the competition.

Note that Boeing did introduce flight envelope protections on 777 and 787. Backporting them to 737 and 747 is in conflict with the mentioned interest to maintain common type rating.

Since the question and some of the other answers especially highlight the stall scenario, there is one aspect which has not been mentioned yet: not only do Airbus and Boeing learn from each other, but there is actually evidence that they also learn together, cooperatively.
In fact, both companies deem the research on stalls so important, that their aerodynamics team join forces in order to find the best strategies for stall avoidance as well as procedures to recover. There is a joint publication titled Stalling Transport Aircraft from 2013 (a web search will also find the PDF), which end with the statement:

The collaboration of our two companies on this paper resulted in a realization that, while there are some differences in the way each approaches stall testing, the vast majority of things discussed are common. While we may be fierce competitors in the sales arenas around the world, when it comes to flight test safety, there is no competition.

In a similar vein, also an article of the Jan 2011 issue of Airbus' Safety First magazine highlights the joint effort in its introduction:

The worldwide air transport fleet has recently encountered a number of stall events, which indicate that this phenomenon may not be properly understood and managed in the aviation community. As a consequence, the main aircraft manufacturers have agreed together to amend their stall procedures and to reinforce the training. A working group gathering Authorities and aircraft manufacturers will publish recommendations for harmonized procedures and appropriate training. This article aims at reminding the aerodynamic phenomenon associated to the stall, and the recently published new procedures.

AF447 was an entirely avoidable situation. Not so much the fault of the aircraft as Air France for not properly training their pilots. Airbus has a simple remedy for loss of airspeed indication at cruising altitude on the A330: five degrees nose up, 85% power, and it maintains cruising speed and altitude. That is, if you don't freeze up and ignore those 'pitot fail' warnings.
A contributing factor may be the high level of automation Airbus uses, which could lull pilots into struggling to handle a situation the automation can't handle... like pitot tubes freezing up.
Same with CA 006 - pilot error on what should have been a simple situation to handle. Lose one engine on a multiengine aircraft, the first thing you do is stabilize the flight attitude by trimming for asymmetric thrust.
The only thing to be learned from either incident is that pilots of large commercial airliners need to be up to date on their emergency procedures training.
Do the companies learn from each other? Given that Airbus spent a fortune developing a bigger 747 and now will probably have to eat those development costs, just as Boeing was moving away from large airliners as not economically viable compared to the large twins like the 777 and 787... no, doesn't look like they're learning from each other.

Your not really answering the question, the last paragraph seems to be more of an afterthought (altho it tries to answer the question) but answer only in a "business" point of view which doesn't really seems to be OP's focus.

Given the large numbers of 747s built, the huge-airplane market segment has been a viable one for some time. The fact that the A380 is not doing so well and Boing is moving away from the big 4-engine planes, does not mean that Airbus is repeating the mistake of Boing, it merely means that Airbus was entering the 4-engine segment a tad too late.

@jjack: From reading the accident investigation reports and their recommendations, it seems to me the investigators do very much look at design of controls, information presentation and numerous other aspects of cockpit design.

@jjack: Maybe bit in the case of AF447, cited in Q, Bonin's actions were inexcusable.

AF447 scenario was faced multiple times by TAM Brazil (today LATAM Brazil) pilots. I have a friend that used to work for TAM and used to fly the A330 as first officer. Multiple times the pitots got stuck and pilots got out of it. He personally never faced it, but the first time this took place, there were internal memos sent out to alert pilots about the risk and reinforcing proper response.
So while the situation was preventable either by preventing the malfunction or by training, pilots are paid the big bucks because they have to know all of those possible malfunction scenarios and have to be able to react to those smartly.
Pilots that depend on planes never failing should never get hired by airlines.
I can point at the deadly B737 rudder problem that crashed several B737s in the 80s, taking many many years to find and fix the problem.
They learn a lot from each other, as well as from their own mistakes.

"Pilots that depend on planes never failing should never get hired by airlines." I'd probably take this one step further, by saying that pilots that depend on planes never failing shouldn't be pilots in the first place. We can only make failures so unlikely (and we have been making great progress in that area); we can't completely eliminate the possibility. At some point something will go wrong with the aircraft, and someone up front will have to react appropriately. For this they need the appropriate training, and the mindset that even though it is unlikely, things still can go wrong.

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Do GPS systems in modern avionics mitigate against spoofing attacks?
There exist a number of different techniques [PDF] to mitigate (or at least detect) GPS spoofing, but the most effective techniques require access to the military-only M-code [PDF]. However, there was a new frequency band added to GPS called L5, which is intended to be used in safety-critical applications such as aviation, but it appears to be geared towards resisting unintentional interference, not spoofing. It can be used to enhance detection, but I'm not aware of whether or not this is done in practice.
Do any modern non-military general aviation GPS systems attempt to mitigate or detect spoofing?

Background: I work in information security and am looking into the feasibility of using aviation-certified GPSes as an auxiliary trusted time source to mitigate time spoofing attacks on computers.

Does this answer your question? Do airlines use GPS for critical purposes? If so, why?

@HiddenWindshield My question is not whether GPSes are used_for critical purposes, but whether they specifically have anti-spoofing mitigations. That question discusses GPS jamming, which is unrelated.

not an answer since I could not find an aviation one, but beam forming and noise detection GPS antennas are a pretty mature tech https://novatel.com/products/anti-jam-antenna-systems-gajt

Not totally convinced that this is on-topic, but absolutely certain that it is not a dupe as suggested. VTLO for now.

@RalphJ OK. I asked the question in The Hangar chat room and it was suggested that this is probably on-topic which is why I asked it here, but if it isn't then I don't mind deleting it, or just letting it get closed.

Looks like you have a good answer below, and if nobody is going to try to close it as off-topic, I won't either. I could see that as going either way, so keeping it open is fine with me. It's most certainly not a duplicate of the other, which is why I posted the comment. Closing it for that reason would absolutely be a mistake.


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How can a VTOL aircraft control yaw while hovering?
I watched this video of a F-35B performing a flight-hover-flight transition and was pretty impressed by the fact that it was able not only to control pitch and roll (which could be, I suppose, performed by differential power from engine and lift fan) but also yaw — while hovering (at 3:15 in the video).

How does it do that? Bleed air ducts from the engines on the sides of the aircraft? (something alike to thrusters used to control attitude of spacecraft I suppose).

There aren't any significant forces on the yaw axis, are there? From what I could see, the only forces acting on the F-35 while it hovers are along the pitch and roll axes, both of which have components in the vertical direction.

Oh I see. Thanks @Pilothead

The rear engine not only can point down, but also side to side. In fact it swivels in both left right and back/forward in addition to moving down through a range of 93 degrees (so you can go backwards).  So the rear nozzle does not just point down. It reacts VERY quickly to pilot inputs. On takeoffs due to the pilot bouncing around, the control stick is moved around a bit - along with computer control to keep the fighter balanced, you see the rear engine gimbals just like a rocket motor. So it moves around (pivots)  just like a rocket motor trying to balance a rocket an that allows twirl/yaw.

In case of F-35, the yaw control during hover (and transition to forward flight) is provided by the Three-bearing swivel module (3BSM), which forma a part of the Rolls Royce Lift System. As Lokheed Martin notes:

Two roll ducts supplied by engine fan air provide roll control. Yaw control is through swivel nozzle yaw. Pitch control is effected via Lift Fan/engine thrust split.

From codeonemagazine

The three-bearing swivel nozzle, 3BSN, design uses three segments of the engine exhaust duct cut on an angle and joined by two airtight circular bearings. ... The forward and aft segments always stay aligned with one another in the rotational axis. The center segment rotates through 180 degrees relative to them. The third bearing is on the back of the engine aft of the turbine stage and provides the ability to swivel the nozzle thrust axis in yaw at any pitch angle.

Consider the nozzle in VTOL position, like below:

By Tosaka - Made by uploader (ref:見森昭編　『タービン・エンジン』　社団法人日本航空技術協会、2008年3月1日第1版第1刷発行、ISBN 9784902151329, 1), CC BY 3.0, Link
If we hold the aft two segments and rotate only the first one, it is obvious the rear segments will rotate along the engine axis, producing yaw by virtue of its position at the rear. There is a slight associated loss in lift produced, but the Digital Flight Control System can easily compensate for it.
Of course, this method of controlling yaw in hover is specific to F-35. In case of Harrier, the reaction control system had 'puffers' at the tail to provide yaw control.

Reaction control system, showing pipes and nozzles for engine HP bleed air.; image from harrier.org.uk

In addition to the vectoring engine nozzles, the Harrier also requires a method of controlling its attitude during jet-borne flight, when the normal aerodynamic surfaces are ineffective. To this end, a system of reaction control nozzles in the nose (blowing down), wingtips (blowing up and down) and tail (down and lateral blowing) are fitted to the aircraft.


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Can this aircraft wreckage be identified?
I live in Salinas (central coast California) and there’s an old plane wreck (located within the boundaries of Toro Park County Park in a remote section). On a hike yesterday, we located and took some pictures and I was seeking some help to identify the type of aircraft and then perhaps some more information (searching the CA plane crash registry came up empty). So looking for more details – firstly identifying the plane and then perhaps locating who/where/etc – there are no other known details.
I have some photos for reference (but would only let me add 1).

Comments are not for extended discussion; this conversation has been moved to chat.

A plane should be able to be identified by the serial numbers of the various parts recovered at the crash scene.  The history of any part on a plane is documented extensively by the serial number.  The NTSB should be able to track down when the part was produced and who the part was delivered to.   As Tanner mentioned the NTSB should be contacted immediately and the wreckage should not be moved.  There are many plane crashes that have occurred many years in the past which have still not been found. You may have stumbled on a piece of history that could bring closure to a family who may have never known what happened to their loved one.

Consider giving the National Transportation Safety Board a phone call. If they don't know about the wreckage already, they might be interested in examining it.
You're not really "reporting an accident", but in any case, the page "Report an Aircraft Accident to the NTSB" says:

Contact the NTSB's 24-hour Response Operations Center (ROC) at 844-373-9922 to file a report.

The tailwheel bracket is from either a Cessna 170 or possibly a Cessna L-19, (which incorporated a lot of C-170 parts, including the tail assembly).  Based on the paint job however, I agree with commenter Zeiss Ikon that the pic is of a C-170 tail assembly.


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What is the airplane type in this formation seen above Eugene, Oregon?

This flight of 2 flew by my house in Eugene, Oregon recently. I assume they're military pilot trainers but I am having trouble coming up with an ID.

Welcome to aviation.SE!

Thanks for the comments and links Redd Herring and YMB.  I had been leaning towards the A29 (EMB 314) and your posted photo of the EMB 312 looks good to me Redd.  I looked at Texans too and even though there were several canopy changes none matched my planes.                                                      The info on Military Tech pretty much cinches it.  They are based at EUG and I live on a 3 mile final to Ry34.  I'm a former controller at EUG and don't recall working these aircraft there so am guessing these are fairly recent acquisitions.

Welcome to Aviation.SE! I put this on the answer you posted but I'll put it here as well in case it gets deleted. If you think an answer is correct you should press the green tick to mark it as accepted rather than post another answer yourself. If you haven't already done so, I'd recommend taking our [tour] and read the [help] so you can see how this site works.

They look very much like Embraer EMB314 Super Tucanos

@ymb1 Perhaps, but it might just be to do with the angle of the photo. The other candidate is the AT-6 Texan II, but that seems to match rather less well.

They are most likely Embraer EMB 312 Tucanos. Military Tech, Inc. has at least 10 registered in Eugene. Here is one in a similar paint scheme:

Source

Wow what are they doing with 10 of those planes in Eugene?  Do the hippies know?  (Real question, the first I mean)

Military Tech is a local group that buys and refurbishes surplus military aircraft.  When I worked at EUG (5 years ago) they were doing mainly helicopters.  It looks like they're expanding to fixed wings.


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In WW2, how did aircraft navigate to the carrier?
In World War 2, how did aircraft navigate to the carrier after their mission? I was thinking of something like a beacon installed in the carrier but wouldn't it reveal the location of the carrier itself?

You are correct. US carriers did indeed have a homing beacon that enabled aircraft to find them.
The carrier transmitting units were called YE or YG, and the receiving units in the planes were designated ZB, and called "Zeebies". The transmitters consisted of rotating "superfrequency" beacons that broadcast different morse letters in different directions that could be decoded by the ZB units, but sounded like static to ordinary listeners. They were installed on all US carriers in WW2.
Here is an excellent summary of the system and its history. More information can be found here and here, and History SE already has a question about it.
The British also had a similar system, installed on a carrier in 1936 and used through the war.
Sources also indicate that the Japanese employed a radio homing system (Hirohito's War by Francis Pike), but I have been unable to locate any details.

It amazes me every time I learn about WW2 techs... thank you for the explanation.

I understand that radio-based homing was available to all carriers during WW2, from the beginning?

American carriers were fitted with a line-of-sight radio homing system, but Japanese aviators were probably limited to old-fashioned dead reckoning, since Japan was less advanced in electronics than the U.S.

This answer could be improved by including references


text:
Does dihedral improve roll stability in gusty conditions?
Against roll instability, should I add more dihedral/a high wing?
I'm trying to build an RC plane that can handle windy conditions. For that I want extraordinary aerodynamic stability.
For longitudinal static stability, I make my planes quite nose-heavy, and compensate for that with a greater tail downforce. That works.
What doesn't work is lateral stability/roll stability. In theory, if a gust rolls my airplane, I will have a sideslip. Due to a high-wing configuration, and a dihedral angle, I will have a rolling moment that will counteract the original roll angle.
Image from avstop.com, modified

So I made my plane attempts have great dihedral/polihedral angles, and a really high wing with a solid surface underneath to further help counteract any rolling.

Any time I went crazy on dihedral and high wings, my planes kept crashing agressively due to very sudden and very powerful side/back flips. At first I didn't understand, as these features should've made my plane almost un-rollable.
However, what I suspect is that these features had the opposite effect. Correct me if I'm wrong, but looking a the first diagram, what I see is that when a plane flying at level flight encounters a sideways gust, it will also make the plane agressively roll over, just as if the sideways gust was from a roll induced sideslip.
Is this a correct assessment? Did these roll stability features make my planes roll around uncontrollably?
Is there a way to have my plane react normally to a sideways gust while having static roll stability? Do I need way bigger vertical stabilizers for these dihedral values?

@quietflyer your answer is very good.  I would qualify "mounting a wing on a slab sided fuselage" by including "with a low CG" in the same sentence (even though you have already mentioned the effects of changing vertical CC placement.  Loved the "larger vertical stabilizer doesn't have time to yaw the plane (which theoretically should help yaw/roll the plane into the gust).  This is exactly what I found with FF models.

Dihedral does not help roll stability to a side force gust.  Quite contrary, a gust will roll the plane into a slip, which then will turn the plane downwind (courtesy of your elevator turned rudder).
Firstly, I would not recommend setting a model plane with excessive "static stability" in windy conditions.  You want to be staticly stable, but not so much that a gust will pitch you up into a stall.  Higher wing loading also helps.
But roll stability from dihedral is good for cruising flight, but no match for a side gust, especially in a model.
What you must do to keep dihedral is to put side area below the CG.  This is known as "anhedralling".  Sea gulls lower their wingtips.  Cessna put the wing (and fuel) on top.  Consolidated built their famous PBY 3 Catalina with the engines on top too!  All 3 want to roll into the wind, not away.  This is the key.
A fourth design, the common paper airplane, does this with gusto.  The side "keel" balancing with the upraised wing around the center of gravity is best for cross wind roll stability.
So you may experiment by raising of lowering your CG, adding side area, and glide testing in a cross wind.  Your second model seems to have more of a chance.  You may try a shorter and more square vertical stabilizer, and a bit of weight (a coin or two) on top of the wing at the expected Center of Pressure.

Makes sense, but I wonder: Doesn't anhedralling counteract the effect of roll stability?

Wing dihedral prevents a plane from rolling on its own.  "Anhedralling" prevents a wind shift from rolling the plane.  So the best way is not to take away your wing dihedral, but to find another way to balance side gust torque around the center of gravity.  Early planes had fixed gear, and shorter (stacked biplane) wings.  Longer single wings, mounted low, had many a designer scratching their head (including me).  So when you test a design in your "wind tunnel", turn it sideways (and from the bottom too).  Know where your CG is on all three axes.

So on your first model, put the bottle on top of the wing, and the prop directly in front or behind it.  (I'm not sure if wearing ruby slippers or chanting "there no place like home" will help).

I dunno-- (re-reading this old answer to a good question)-- it seems to me like any given design feature either increases "effective dihedral", or decreases "effective dihedral" (or in extreme cases makes the effective dihedral go negative, i.e. creates "effective anhedral".)  I'm having trouble with this idea that there's any particular benefit to simultaneously adding various features to increase and decrease the "effective dihedral".  At the end of the day, the "effective dihedral" is what it is, regardless of whether due to a bunch of competing features, or otherwise--

Also having trouble with the idea that choosing a high wing placement generally tends to decrease "effective dihedral", due to fuselage side area below CG.  In practice, I believe that that's not the dominant factor that determines the "effective dihedral" influence of a high-wing design.  Moving the wing higher on the fuselage usually tends to increase effective dihedral, not decrease, for reasons that have been discussed elsewhere on ASE to some extent (if not adequately so, could be the basis for a new question... )

Less controversial would be the observation that lowering the CG (e.g. moving the heavy bottle downwards) always tends to increase effective dihedral, and raising the CG tends to do the opposite-- especially if this can be accomplished without other huge changes in the shape of the model as "seen" by the airflow/ relative wind-- (e.g. a small bottle full of lead shot rather than a larger one full of water) -- also +1 on the idea that excessive stability in either pitch or roll axes is not helpful in gusty conditions!

@quietflyer well, certainly enough in comments for another answer.  But one aspect of the high wing "conflicting" anhedral and dihedral design features is they (being generally farther from the CG) might tend to make the effects of a sidewind gust slower and easier to control, hence the "trainer" design.

You actually want the (real) dihedral to mitigate an accidental roll input error from the pilot (which can be corrected quickly before the plane slips too much), whereas the (barn door) side area of the high wing should roll the plane into a sustained gust.  The give and take is a sustained roll will lead to (the dreaded ) spiral instability.  That's the trade-off in the "trainer" design.  Seen plenty of these "go in" at the R/C field too when I was learning.

I think you’re having a classic dilemma of static directional stability vs dihedral effect. There is always a compromise between the two. Increasing dihedral makes spiral mode more stable. But this has a side effect, which is less stable dutch roll. Moreover, in extreme cases, dutch roll may even become unstable. The side flips you are describing sounds like an extreme unstable dutch roll mode, which eventually may end up in uncontrolled flight.
If you are unable to reduce the dihedral effect, one other fix you can apply is to increase the directional stability by increasing the effectiveness of the vertical stabilizer. Even though, that fix makes the aircraft less stable in spiral mode, it’s almost always preferred to have a spirally less stable aircraft than the one that has unstable dutch roll. Because, a pilot can easily stop the effects of an unstable roll by ailerons. However, stopping an unstable dutch roll can get a little bit tricky and even dangerous in large airplanes, especially under stress.
So I recommend initially, reduce the dihedral effect. If that's not possible then increase the vertical tail effectiveness (read: volume) ( volume = v.tail area x distance to cg).

Correct me if I'm wrong, but looking a the first diagram, what I see
is that when a plane flying at level flight encounters a sideways
gust, it will also make the plane aggressively roll over, just as if
the sideways gust was from a roll induced sideslip.

That's correct.  The "positive effective dihedral" generates a "downwind" roll torque in both cases, in relation to the "relative wind".

Is there a way to have my plane react normally to a sideways gust
while having static roll stability?

Just go easy on the dihedral, or on other factors that contribute to "positive effective dihedral" (e.g. high wing placement, low C.G. placement.)  "Overdoing" these things, especially in combination, will give you way too much "effective dihedral" which will make your plane much too vulnerable to the immediate effects of strong sideways gusts.  And see the comment below about the benefit of reducing the size of the vertical fin.

Do I need way bigger vertical stabilizers for these dihedral values?

I don't believe that that's going to help you.  And contrary to another answer, I don't believe that you are experiencing classic "Dutch Roll".  I think you are just seeing your plane suffer from the immediate effects of strong gusts, due to excessive "effective dihedral", and likely due to excessive positive longitudinal stability (pitch stability) as well.
For any given desired degree of positive roll stability, you can get away with less "positive effective dihedral" geometry -- specifically meaning that the aircraft will generate less "downwind" roll torque at any given sideslip angle-- if you reduce the size of the vertical fin.   This will allow the plane to experience more sideslip in the long run, so that whatever "positive effective dihedral" is present will be more effective at generating a roll torque to roll the plane back to wings-level.1
Look at it this way-- if you want to increase the plane's degree of positive roll stability, you can either increase the degree of "positive effective dihedral", or you can decrease the size of the vertical fin.  Either alteration will help the plane come back to wings-level in the long run.
And to a first approximation, we might think that either alteration also might make the plane have a greater tendency to roll "downwind" immediately after being struck by a sudden side-gust.  But that's not really true.  In the short run, the effects of the two alterations will have very different effects on the way the plane reacts to a sudden side-gust.  Because when the plane is struck by a transient side-gust, it doesn't have time to yaw into alignment with the airflow (relative wind) before the "positive effective dihedral" generates a strong "downwind" roll torque, so an overly-large fin won't do much to minimize the aircraft's immediate (downwind) roll response in this situation.
So for best stability in gusty conditions, keep the vertical fin as small as you can, and go easy on the "positive effective dihedral" as well, only designing in the minimum amount needed to slowly return the aircraft to wings-level after a disturbance.  The smaller the vertical fin you can get away with, the less "positive effective dihedral" you'll be able to get way with as well, and still have the plane slowly roll back to wings-level after a disturbance.
Generally speaking, all these factors tend to shift the "effective dihedral" in the positive direction:
Low CG placement relative to overall shape of aircraft
Wing mounted directly on top of fuselage, especially a slab-sided fuselage.  (To some extent a similar extent is generated by putting the wing on a pylon of substantial length ("chord").)
Actual dihedral in the wing (or tail)
High-mounted vertical fin
Naturally, an important question that would help you choose from the various different solutions that have been offered in various answers, is "how does the plane fly in smooth air?"  True "Dutch roll" instability should manifest itself even in smooth air, especially in response to certain initial control inputs.  If you do find that to be occurring, then this answer may not be the right one for your situation.
Footnotes:

To understand why "positive effective dihedral" tends to return an aircraft to wings-level after a disturbance, we have to understand that a) all turns tend to involve some amount of sideslip (toward the inside wingtip, so that a "yaw string" would blow toward the outside wingtip), at least in the absence of a "coordinating" rudder input, and b) sideslip interacts with positive effective dihedral"-- no matter exactly what the specific source of the "positive effective dihedral" geometry is -- to create a downwind roll torque, which in the absence of gusts, tends to return an aircraft toward wings-level.

Locking to stop the usual constant edit cycles. Formulate your thoughts, make a single additional edit in an hour (if needed) please.

Well, all I can say, is that no one can accuse me of editing for the purpose of trying to "bump" the answer up to the "top of the stack", since not one single change to any other other ASE question or answer appeared during the brief time before the question was locked, so no other question or answer was "bumped" down by even one single "slot". Something to think about. Why a few edits during a brief time period are so disturbing to folks, I don't understand, but obviously from the upvotes to the comment, somehow they are. Just one of those mysteries of life I guess. –

And btw more or less similar logic applies to this (locked) question https://aviation.stackexchange.com/q/98210/34686 -- Yes some edits were introduced Mar 22-23, after the question was posted Match 19-- in part specifically in response to feedback from other ASE users. Nowhere is there evidence of a trivial edit designed to "bump" the question back up to the front page. Why this suddenly came to mod attention on March 29, six day after last edit to question, is unknown to me


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What does "share a type rating" mean?
The Boeing 787 shares its type rating with the 777, but what exactly does that imply?
Surely it cannot mean any 777 pilot can just jump into a 787 and fly it. While being similar, the 787 has some different systems, most notably bleed-less engines.
I assume it means something like a reduced course to switch to the 787 instead of a full type rating. But then again, Airbus advertises how easy it is to switch between different Airbus aircraft (see "Benefits for Pilots" section in https://www.airbus.com/aircraft/passenger-aircraft/commonality.html), so shouldn't they all share the same type rating then?
So what are the limits for "same type rating"?

It means the transitional training for 787 is grossly simplified, if pilot is certified for 777.

Can we assume you're asking about EASA/Europe? In the US, the FAA appears to have two different type ratings.

Yes, EASA uses a single "licence endorsement" (see p. 5 in https://www.easa.europa.eu/sites/default/files/dfu/20180712%20EASA%20T_R_List_Acft.pdf)

If two aircraft (let's call them Aircraft A and Aircraft B, since this isn't specific to 777/787) share a type rating (technically known as a "common type rating"), it means that, if a pilot is already certified to fly Aircraft A, and wants to get certified to fly Aircraft B, they only have to take a course on the parts of Aircraft B that are different from Aircraft A.  If Aircraft A and Aircraft B didn't have a common type rating, an Aircraft A pilot wanting a certification for Aircraft B would have to train for every part of Aircraft B, even if many, or even most, of those parts were exactly the same as on Aircraft A.
As you can imagine, getting two (or more) aircraft types a common type rating can save quite a lot of training time and money for pilots switching from one to the other.
Grossly-oversimplified example

Our aircraft:

Aircraft A is composed of parts A, B, C, D, E, and F.
Aircraft B is composed of parts A, B, C, G, E, H, and I.

Our pilots:

Grace is certified to fly Aircraft A.  She wants to become certified to fly Aircraft B.
Tedd is certified to fly Aircraft B.  He wants to become certified to fly Aircraft A.

Scenario 1: Aircraft A and Aircraft B do not have a common type rating

To gain certification for Aircraft B, Grace has to take courses on parts A, B, C, G, E, H, and I.
To gain certification for Aircraft A, Tedd has to take courses on parts A, B, C, D, E, and F.

Scenario 2: Aircraft A and Aircraft B share a common type rating

To gain certification for Aircraft B, Grace only has to take courses on parts G, H, and I.  She doesn't have to take courses on parts A, B, C, or E, since those parts are the same as on Aircraft A, which she's already certified on.
To gain certification for Aircraft A, Tedd only has to take courses on parts D and F.  He doesn't have to take courses on parts A, B, C, or E, since those parts are the same as on Aircraft B, which he's already certified on.

Real-world example
The A330 and A350 share a common type rating (but the A340 doesn't, because different number of engines); as a result, whereas (say) a 767 or A300 pilot wishing to gain A350 certification needs 23 days of comprehensive training on every aspect of the A350, an A330 pilot has to take an eight-day course to become an A350 pilot.  This eight-day course, covering only the parts of the A350 that differ from their counterparts on the A330, is, appropriately enough, termed "differences training".  (Source)

Thanks for the clarification. If I understand you correctly, an A320 pilot still needs to do the full training when transitioning to the A350 then?

@Bianfable: Yes; it's easier than transitioning from (say) a 767 to an A350 would be, since (like you said) Airbus keeps their aircraft fairly similar cockpit-wise, but, since the A320 and A350 don't have a common type rating, your A320 pilot still needs to take just as long of a course as a 767 pilot would need to before either of them can fly A350s.

This answer has a problem: it is not necessary for planes to share a type rating to benefit from a shorter training class. For example, an A330 to A340 class is much shorter, 7 days, even though they don't share a type rating. My understanding too is if you do initial A330 and A340 training simultaneously, the additional time is as small as 3 days. The real benefit to sharing a type rating is currency: requirements between the two models are pooled.


text:
Are there any limitations of diopters (corrected eyesight) in the US?
According to FAA standards, there seems to be no diopters limitation for a first class medical.
I'm Japanese. JP CAC limits it. UK CAA also does.
I would appreciate it if you could tell me whether my understanding is mistaken or not.

The FAA bases their eyesight limitations on total acuity and not on diopter correction strength. Although many people equate these as being the same thing, they are not.
Diopter correction is based on focal length. How well an image is focused onto the retina of your eye. An image not being focused on the retina is usually due to a distortion of the cornea. Either it is too curved or not curved enough. The image focal point can be on, prior to (cornea too curved), or after (cornea too flat) the retina.
The cornea might also not be completely spherical. More like a rugby ball and less like a soccer ball. This is called astigmatism.
Sometimes the issue could be with the lens. The stiffening (reduction of flexibility) of the lens due to aging is usually the cause of the need for bifocals and reading glasses. The lens can no longer adjust its own focal length as well as it used to. Making it harder to focus up close.
Misalignment of the focal point with the fovea due to a tilting or shifted cornea, lens, or retina is a prismatic issue. The inability to physically align the eye (lazy eye or amblyopia) can also cause this.
Acuity is based on how well the image can be distinguished clearly regardless of focal length. An image can be focused on your retina (0 diopter correction), and still not be clear or distinguishable. Eye diseases like cataracts (fogging or frosting of the lens), glaucoma (increased internal pressure of the eye pressing on the retina, causing damage), macular degeneration (damage to the fovea of the retina), etc. can degrade your acuity without affecting your focal length. No glasses of any diopter strength will improve acuity in these cases. Even eye injuries like a corneal ulcer or a scratched cornea can negatively affect the acuity of a person with normally perfect vision.
Although all of these issues affect acuity, all of them together add up to total acuity. Using only one measure can not accurately determine a pilot’s ability to see correctly. Diopter correction alone can not tell the entire story.


text:
How does altitude affect drag?
Consider two aircraft. Aircraft A flying at sea level with weight (W) and Angle of attack (α). Aircraft B flying at altitude h in level flight at the same weight (W) and same angle of attack (α) (same configuration as Aircraft A). Will the drag experienced by both the aircraft be the same?

Or this: Why are true and indicated airspeed different?

Approximately, yes.
Both lift and drag depend on the density of air, so in order to generate enough lift at the same angle of attack in thinner air, an aircraft has to fly faster. Thus the same number of air molecules hit the plane every second and the drag is approximately the same.
This is a bit of a simplification (especially the bit about drag being caused by air molecules hitting the plane) as the change in temperature causes a slight change in viscosity, which affects one type of drag (detailed Peter's linked question). However it's a good enough approximation for most pilots, who use 'Indicated Air Speed' as a air-density-independent guide to aerodynamic speed.


text:
How much thrust does the Lilium aircraft produce?
I have been researching the Lilium aircraft and can’t find information about thrust. An early version of this aircraft was 2 seats with a loaded weight of 1,400 lbs, 36 ducted fans and 320 kW peak power. They are testing a five seater also for vertical takeoff. Either the standard calculations for thrust are wrong in ducted fans or something else is going on. Any guesses?

Related and worth a quick look

The highest thrust is normally needed during hovering. During hovering thrust equals weight so the thrust generated by each fan should be simply:
$weight/nr_{fan}$
Since in these designs the total failure of some fans is always taken into account, $nr_{fan}$ is the minimum number of them which can sustain the flight (let's say some 80% of the total number). For the lilium, I suppose a bit more of thrust is needed during the transition to forward flight so the previous value has to be increased, let's say of some 10%. Obviously this final value doesn't take into account any aerodynamic interference
EDIT
Just out of curiosity I did some basic calculation. The thrust generated by an ideal not-ducted rotor is:
$ T = \sqrt[3]{2 \rho A P^2} $
For a ducted rotor this increases of some 30%, the power being equal:
$ T = 1.3 \sqrt[3]{2 \rho A P^2} $
From the pictures of the aircraft I would say that each rotor has some 20cm diameter and therefore $A$ becomes:
$ T = 1.3 \sqrt[3]{2 \rho (0.8*36 \pi 0.1^2) P^2} $
where the number of rotors (36) has been multiplied by 0.8 to take into account the possibly failed rotors.
As said the max needed power could be some 10% higher than in hover to cope with the transition from hover to forward flight:
$ T = 1.3 \sqrt[3]{2 \rho (0.8*36 \pi 0.1^2)*(P/1.1)^2} $
In hover thrust equals weight $T = W$. Using the ISA value for $\rho$ and the official 320kW for the total engines power we get some:
$ T = W = 737kg = 1620lb $
which correlates quite well with the given max takeoff weight of $1400lb$


text:
Where does the MiG-29 store fuel?
How does the MiG-29 fuel system work? Like, where does it store around 300 cubic feet of fuel?
Also, which fuel does it use? Is JP4 preferable?

I'll comment on the "also" question, as it's not worth an answer. MiG-29, like most Russian/Soviet jets, normally uses the TS-1 kerosene. It's closest common analog is Jet-A1, but like anything in aviation, every type of fuel has to be specifically approved. Jet-A1 and JP-8 are approved, AFAIK. I'm not sure about JP-4, but it's certainly not 'preferable'. In practice though, a jet engine will burn almost anything, and in times of war you can even use diesel fuel.

Like every plane, the MiG-29 stores its fuel in fuel tanks ;)
On a more serious manner:
Generally speaking, there are 6 internal fuel tanks: 4 distributed around the fuselage and 1 in each wing.
Later versions (namely the SMT) have larger internal fuel capacity thanks to the enlarged spine.
The exact locations of these tanks can be seen in this cutaway (src): 63, 72, 93, 107, 187.
In addition to these, the 29 can also carry 3 (1 in the very early versions) jettisonable external fuel tanks.

can you please share a picture?

@AdeelAhsan Please try a simple web search for "Mig 29 fuel tanks", this is a topic with many existing answers and resources.

@AdeelAhsan a picture of what? I provided a link to a very detailed cutaway.

you  should also mention external fuel tanks (that can be jettisoned).

To avoid link-rot, you should include the picture (with attribution) in your post.

@ManuH updated..

Please note that on later models the upper air intake functionality (#55 that gill-like part) got removed, so those have more space for fuel.

The aircraft is equipped with seven (7) integral fuel tanks:  five (5) Center body fuel tanks and two (2) wing tanks.  Center body fuel tank #2 serves an an engine feeder tank with all other tanks transferring fuel to it via a network of fuel pumps for consistent weight and balance.  The aircraft can be refueled by means of a single pressure refueling receptacle located in the port main landing gear well.

(Source: Luftwaffe MiG-29 Flight manual)

Thanks this is the explanation I was looking for


text:
When resetting the heading indicator to match the magnetic compass, do I need to use the compass deviation card?
At least every 15 minutes we set the Heading Indicator's number to match the number of the magnetic compass.
In this situation, should I consider the deviation card below the compass card or not?

Welcome to aviation.SE!

If you have an electronic DG like the Garmin G5, you specifically don't want to do this because it's already compensated, but then again you don't need to set it every 15 minutes either.

Yes the DG is supposed to be set to the corrected magnetic indication whenever you set it, so you should mentally add or subtract the degree or two or three based on the closest segment on the card as a standard practice.
I agree with Michael however that it's not really that big a deal for VFR flying in the real world, especially in the age of GPS where you can just adjust heading based on GPS ground track on your phone or a tablet to go from A to B and you don't even really need to look at your compass (although, you might suddenly find you need it, so don't neglect it).
If you were doing old fashioned dead reckoning navigation, precision in holding a heading is important.  Or in the IFR world where you have to fly headings in a clearance.  Even there though, the allowable calibration error on a compensated (that is, WITH the deviation accounted for) compass is +/- 10 deg (!), so the little 2 or 3 degree calibration card can be quite a bit off anyway and still be legal.

Personally I never bother, but then when I fly an airplane with a Directional Gyro that needs adjustment I am always VFR, and generally know right where I am going so I am not relying on a super accurate compass.  (I know the Puget Sound area where I typically fly very well, and there are lots of excellent visual reference points)  Also, plus or minus a few degrees is a little tough to even see on those small dials.
However, if you are working on an instrument rating, or already have one and are getting ready to shoot an approach, or are navigating on an airway, I would definitely get in the habit of accounting for the deviation.  At least acknowledge the issue and make an attempt, especially if flying with a CFI or DPE.
Just remember the adjustment is temporary because it will drift away from your compensation shortly, so don't focus on dialing in that extra one or two degrees of accuracy at the expense of other essential tasks if you are overloaded.

Even in the VFR world you should reset your DG from time to time. That’s especially true if you are doing training maneuvers like steep turns or turns around a point which make your DG precess more than normal. Then, if you are on flight following and ATC gives you a heading to fly to avoid other traffic you are flying in the right direction.

I agree, and I do.  I just don't take the extra time to fine tune it to the compass deviation card.


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XFY-1 Vertical take-off mechanics
Hi I saw this video the other day of an XFY-1 doing a vertical take-off and landing and moving left to right while hovering.
See the video Here.
After watching this I had a few questions on how this is accomplished.

How does the plane go from vertical to horizontal and from horizontal to vertical flight? Is this done by moving the elevators to their respective extremes.
How can the plane move left to right forward to back while in vertical mode?
Is this done by some sort of helicopter rotor type of contruction in the props?

I am not sure if this is the right place to ask, neither am I an expert when it comes to planes or the engineering behind them (I just know the basics).
Would love to know how this works or resources that explain this, could not really find any myself :)

The plane takes off vertically, with the prop wash blowing over conventional control surfaces. To tilt forwards the pilot pushes the stick forward in the usual way to "lower" the elevators and tip the nose "down". As the plane tips progressively over, it progressively gains flying speed and lift transfers to the delta wings. At the same time, the elevators are brought back to the level for conventional flight. Landing is the same thing in reverse, with the elevators being raised.
Manoeuvring in vertical mode is again just the same, but only a small control movement is needed for a gentle tip in the right direction: elevators in one axis, rudders in the other. The elevators also act as ailerons, which allow the pilot to gently spin the plane round even when vertical.

Transition must have been very difficult, and landing with a stiff wind short of impossible. No wonder only one prototype was ever flown...

Yes. The pilot's seat was on gimbals and swung forwards by 45 deg in vertical mode. But even so, flying it was so difficult that its test programme was abandoned part way through.

The control surfaces are in the prop-wash, and so are effective even when the aircraft is standing still. To manoeuvre the aircraft all you do is tilt the fuselage, which tilts the prop and thus tilts the lift/thrust just like a helicopter does.

just to make sure I understand correctly. So the plane is able to do all this just by using its elevators and rudder to tilt the fuselage in the desired direction. Right?

I'm pretty sure the answer is  "yes, right".  I bet there was a second rudder on the down-projecting (ventral) vertical fin as well though you'd want to double-check that.  And technically the elevators should be called "elevons" because they also have an aileron function.  If there really were two rudders, then the rudders could also have been mixed for roll control and thus be "ruddervons" but my guess is that they didn't bother with the complexity that would entail.

I suppose you are aware that a similar plane developed at the same time had, rather than delta wings, straight wings located near the CG plus a big cruciform tail.  Same basic principle.  With the ailerons possibly not being in the propwash, it would be interesting to know exactly how roll control was accomplished while hovering-- elevons and/or ruddervons, despite the moment-arm for roll torque being much shorter than with the XFY-1?  Could be grounds for another question...

It would be more correct to just call all the control surfaces "attitude control vanes" when in hover mode since they all perform the same function.  Really no different from having control vanes in a rocket exhaust in a rocket that was able to hover.

@FutureCake Go look on YouTube for videos of R/C pattern (especially indoor pattern) aerobatic aircraft.  Many of these can hover, maneuver, and transition into and out of hover without even a contra propeller system to cancel engine torque.  They do it the same way -- using the conventional surfaces in prop wash to both cancel torque and vector thrust for low speed translation; they also have >>1 TWR so they can accelerate upward out of the hover to transition a bit more positively than the XFY-1 did.

@quietflyer That other VTO plane used, IIRC, differential pitch in the contra props for roll control while in hover.

Thanks all for all the great extra information in the comments!


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Can a part 103 ultralight weigh 400kg fully loaded?
I am designing an electric VTOL personal part 103 ultralight.
My question is: I have 114kg for the ultralight, 100kg for the pilot and 30kg for the baggage. About 260kg is enough to be take off safely but I want to design it up to 400kg.
If I do that, will it still be accepted as a part 103 ultralight and what is the weight limit for it?

Part 103 limitations pertain to dry weight in takeoff configuration, maximum stall speed, maximum level flight speed, and maximum fuel capacity.  They do not directly address maximum gross takeoff weight.
However, weight affects stall speed, and I'm not certain how Part 103 defines its stall speed limit -- whether they specify at some minimum operating weight, or at "design weight" or some other value.  The complete regulation is available online, however, so you can read it yourself and determine if you'll be able to design for your maximum 400 kg GTOW.


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What is the maximum takeoff weight allowed for a part 103 ultralight?
What is the max takeoff weight (MTOW) for a part 103 vertical takeoff (VTOL) ultralight?
And is the value peak or continuous limit?

14 CFR 103.1
The FAA currently does not discriminate between "VTOL" and "normal" ultralight aircraft, nor between gas-powered or electric. The aircraft, if powered, cannot weigh more than 254lbs "empty" weight excluding floats and safety equipment that deploys in an emergency situation.
I'm not sure what you mean by "peak limit" or "continuous operation". The aircraft, when weighed without liquid fuel, must be less than 254lbs. It can carry up to 5 US-gallons of fuel (which can add up to 30lbs).
There is no limit to the MTOW for the aircraft though, it can carry a 400lb individual if you can make it fly, but it can't carry more than 1 person. So if the aircraft weighed 253lbs, you were 400, fuel is 30 that is 683lbs and still legal under Part 103. (Depending on how liberally you want to apply the "single occupant" rule, you may try to squeak your 200lb Mastiff aboard as well)

There is no "gross weight" limit as far as I can find in the regulations.  I think the thing you need to be concerned about is Power off stall speed.  The regulations do state a 25 knot limit on power off stall which has to do with wing loading.  If you have a high wing loading (high weight to wing area ratio) then your stall speed will be higher.
So the question is what is YOUR Gross Weight based on your wing area, weight and lift coefficient and air density.  So you need to "work backwards" with the stall speed formula to determine the gross weight for your aircraft.
SkyClimber


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How can I certify an ultralight design as complying with part 103?
Can you help me about which procedure do I need to follow in order to have a certificate that my design is part 103 ultralight.
And as a information how long would it take to get the certificate and about how much?
What would be the first step?
Thank you.

Unless you plan on quantity production, you may be overcomplicating this -- there are lots of legal Part 103 craft flying that are one-off, so the process can't be too hard.

@ZeissIkon Commercial production of an uncertified product does not need any type of certificate either and there is no process.

No certificate needed and "satisfactory evidence" is only needed "upon request". From the FARs:

103.1   Applicability.
This part prescribes rules governing the operation of ultralight vehicles in the United States. For the purposes of this part, an ultralight vehicle is a vehicle that:
(a) Is used or intended to be used for manned operation in the air by a single occupant; >(b) Is used or intended to be used for recreation or sport purposes only; (c) Does not have any U.S. or foreign airworthiness certificate; and (d) If unpowered, weighs less than 155 pounds;
or (e) If powered: (1) Weighs less than 254 pounds empty weight, excluding floats and safety devices which are intended for deployment in a potentially catastrophic situation; (2) Has a fuel capacity not exceeding 5 U.S. gallons; (3) Is not capable of more than 55 knots calibrated airspeed at full power in level flight; and (4) Has a power-off stall speed which does not exceed 24 knots calibrated airspeed.
§ 103.3   Inspection requirements.
(a) Any person operating an ultralight vehicle under this part shall, upon request, allow the Administrator, or his designee, to inspect the vehicle to determine the applicability of this part.
  (b) The pilot or operator of an ultralight vehicle must, upon request of the Administrator, furnish satisfactory evidence that the vehicle is subject only to the provisions of this part.
103.7   Certification and registration.
(a) Notwithstanding any other section pertaining to certification of aircraft or their parts or equipment, ultralight vehicles and their component parts and equipment are not required to meet the airworthiness certification standards specified for aircraft or to have certificates of airworthiness.

Need to start from a point but from where dont know yet, want to apply for my ultralight in order to be able to sell as a comertial part 103 ultralight.

@AliMa You can't apply for something that does not exist.


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How does the wraparound wing design reduce drag?
How does the wraparound wing in this AOPA article reduce drag?  One would think all that extra leading edge and surface area would make it worse.
One more link also.

The Parsifal Project has produced a proposed design dubbed PrandtlPlane, an homage to Ludwig Prandtl who developed an idea for an airplane wing that boosted efficiency (and reduced drag) by wrapping around on itself to form a box around the fuselage.

This paper on Conceptual Design of High Subsonic Prandtl Planes
Title: Conceptual Design of High Subsonic Prandtl Planes
Author: Zohlandt, C.N.
Contributor: La Rocca, G. (mentor)
is also proving to be most interesting reading

It does not reduce drag, but creates more of it.
This concept is called a "box wing" and is one variety of closed wings.  Another is called a "joined wing" and was popularized by Julian Wolkovitch. However, only people who don't understand how a wing produces lift can be enticed by this concept - it has too many drawbacks for the modest reduction in induced drag it offers. The general idea is to sweep the horizontal surface of a T-tail forward and stretch it out until it joins the backward-swept wing and relieves it in bending, similar to a strut.
Similar to winglets, the vertical extension of the wing structure will involve more air into the production of lift, which reduces induced drag, but this extended structure must be bought with a hefty mass increase which will reverse the gain in induced drag, because much more lift needs to be produced in order to lift the additional structure.
Note especially that the rear wing (which is supposed to act as a tail surface) will be loaded in compression in order to support the wing. Making this rear wing narrow will make it susceptible to buckling, which can only be avoided by a stiff and heavy structure, and will increase its friction drag due to its much lower Reynolds number. When a winglet-like element is added between wing and horizontal tail, this winglet is now loaded in bending and will also need to be made much stronger and heavier than a conventional winglet.
Calling this a "Prandtl plane" is to completely misunderstand the 1924 publication of Ludwig Prandtl, who very well understood how wings create lift, about the benefit of box wings.

It behaves like a wing with a higher effective aspect ratio, thanks to the wingtips going full circle, while fitting into smaller overall dimensional restrictions. This wing can also be thin without suffering as much structural weight penalty as a normal wing would thanks to the bracing effect of its box shape (but there needs to be more angle between the wings than in the picture  to get significant structural improvement).
The price for that is that is still adding weight and becoming a tandem wing with possible interference between upper and lower surfaces. Is it better overall? It appears that the general case is no, but it most likely has its niches where it's better.
There's been a related question: Do box-wings suffer from induced drag the same way as normal wings? - that has a lot more detailed information in the answers. Be sure to check it.

Bottom line, it's a tandem wing with a little fin joining the tips.  Basically a variation of this contraption, which does fly, more or less.
https://en.wikipedia.org/wiki/File:Henri_Mignet_HM_14.jpg
Truth is, there isn't a hell of a lot under the sun in aviation that wasn't already thought up by the 30s.


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Is the term "small" applied differently between piston engine planes and jet engine planes?
My understanding was that "small" covered planes up to 12,500 pounds, no matter the engine type.
Would that be gross weight/max takeoff weight?
Brought to mind by the two recent Cessna Citation crashes (Cessna 560, Cessna 680A), and head lines of "Small  jet crashed during takeoff"  and "Small jet crashed during landing". Pretty sure their gross weights, 15900 lbs and 30800 lbs would push them out of the small category.
Luckily, all crew and passengers were able to walk away in both accidents.

Related: Is there a definition of light/medium/heavy aircraft? From that Q&A I read it as MTOW. I'd guess when a newspaper writes about a "small airplane" then they probably don't have ICAO or FAA regulations in mind but simply common sense, like "up to 10 seats", "up to 150 seats" and "(way) more than 200 seats" or something similar which is comprehensible to laymen.

So that link would suggest "Medium" then:  (E) Medium: Small commuter aircraft including business jets weighing more than 12,500 up to 41,000 lbs such as the Embraer 120 or the Learjet 35;   The news couldn't even get that correct.

"Light" is a category with a specific criteria (MTOGW 12,500# or less). "Small" is simply an adjective, applied subjectively and without a similarly clear definition. Especially when used by reporters.

On hold for an FAA terms definition? Really?

I wouldn't expect press headlines to adhere to the FAA or ICAO definitions of "small", "large", "heavy", etc. This would be a public vernacular definition of "small", which would distinguish from the big airliners most people think of when hearing about jet planes.


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Why are pilots asked to provide a reason for a go-around?
Why does the tower ask pilots what the reason is for a go-around? This seems to be standard for commercial flights.

I've never been asked for a reason for my go-arounds.   I assume its because I'm in Cessna-172s, and sound like a low-hour, inexperienced pilot on the radio.   (I go around at the slightest indication the approach is a little bit off.)

Pilots are not required to give a reason for a go-around, just to say that they are going around. A go-around is a busy time for the pilot(s) of the aircraft - power, flaps, trim, must be set, gear raised in some cases. The pilot needs to aviate first.
The tower wants to know why the go-around was initiated by the pilot as it may be relevant for safety and/or operations. If the pilot is going around because of a botched approach then that won't impact other flights, however if there is a problem with the aircraft the tower can organize emergency resources. If the go-around is due to a situation on the ground then the tower can look to clear that up.

You'd think if there were an emergency situation then the pilot would feel duty-bound to report it regardless of being asked. But I guess it's better to be explicit and deliberate about this stuff.

If there's an emergency the pilot may be too busy dealing with it to report it right away. The first priority is to maintain control of the aircraft. Once that's done the pilot will call ATC.

"The tower wants to know why the go-around was initiated by the pilot as it may be relevant for safety and/or operations. If the pilot is going around because of a botched approach then ..." ... what does the pilot say? "I botched the approach" ? :-)

The reason 1 pilot goes around may also be the reason the next pilot goes around, The second pilot would like to know before hand whether the runway is safe to land on.
For example if it is wind related he can delay landing until it dies down.
If it is debris related then the tower can dispatch a cleaning crew.

On the other hand if it is inside the cockpit, perhaps the crew could use some assistance like delay vectors to work checklists and the tower wants to know as soon as practical as well.

Are we assuming VFR here? It would be nice to know if the weather goes below minimums. It is against regulation to begin an approach when the weather is below minimums - not to mention the potential waste of gas on missed approach.

I've only heard ATC ask IFR flights why they went around/missed, and I assumed it's because ATC may not be able to see the plane (or even the runway) in IMC, so they need to know if it was because of something that could affect following planes. For VFR flights, it's usually obvious why the plane went around, e.g. a student in the pattern is expected to go around now and then.

The only reason for a go-around is that the pilot or ATC thinks that landing is not safe or possible for this approach.
When the pilot does that, they follow the  5 Ups memory aid (Power Up, Nose Up, Gear Up, Flaps Up, Speak Up). You can see that by the time a pilot is ready to inform ATC about go-around, he is already going around.
Commonly, when ATC requests a go-around, it is if there is an unsafe condition such as an aircraft, vehicle, or object on the runway.
When the pilot decides to go-around, it can be one of the following reasons:

the aircraft is not lined up
it is not configured properly for a safe landing
an aircraft, vehicle or other object has not cleared the runway
no landing clearance was received (at a towered field)
the landing gear is not properly extended
a dangerous meteorological condition is experienced on final approach (e.g., poor visibility, excessive cross-winds, windshear, etc.)
excessive energy (too high or too fast)
or any other unsafe condition is detected

Student pilots often need to practice missed approach procedures, but in that situation the tower will have been informed of the student's intentions beforehand (probably before the student even took off), and it's wise for a student pilot to not be doing this kind of practice on the main runways of a class B or C airport.

@KeithS If a student pilot gets a chance to land at a Class B or C airport, ATC will not let them use the main highway anyway, for practicing go-arounds. Of course unless you say please.

Most Bravo airports are too busy to accomodate student pilot practice to begin with. DFW's kind of persnickety about this; they're the busiest airport in the U.S. by aircraft takeoffs/landings, and they're not going to let some yahoo toodle around in a left-hand pattern tying up time on approach/tower frequencies (and the GA runway). That goes double when the winds aren't north/south and the entire airport runs on its two oblique runways; 13L/31R becomes the runway for the entire left half of the airport.

You want to practice approaches, there are 11 Class Ds in the Metroplex that can help you practice approach procedures with comms, and dozens of untowered strips to practice the cockpit procedure (power, pitch, flaps, gear) while only having to notify "traffic" of your missed approaches.

This is a good summary of the reasons for pilots deciding to go around, but I don't see where it addresses why the tower is asking for the reason.

@fooot When a pilot decides to go-around, there is a reason. ATC probably asks for it so that it appears in the recordings, for any future reference. ATC recordings can be used for several different reasons (see this and this). With the digital technology available now, recordings can be kept for a lot longer than tape alternatives.

@KeithS One slight nitpick: DFW actually isn't the busiest by movements. O'Hare and Atlanta run pretty much neck-and-neck for that title, while DFW is a fairly distant #3 (not just in the U.S., but in the world.) The 10 busiest are, in order: O'Hare, Atlanta, DFW, LAX, Beijing Capital, Denver, Charlotte, Las Vegas, Houston (IAH), and Heathrow.

Short answer: because first you're disrupting the traffic pattern (especially at larger airports that don't use a circular pattern and coordinate direct approaches instead) and the tower will want an explanation, and second because if there is a problem outside the cockpit causing you to execute the missed approach, other craft might have the same problem, and if the tower knows about it they can take steps to resolve it, or at least advise other incoming craft.

The tower does not need anything to cover their backsides. Going around is a standard fail-safe that they have to expect and have procedure to handle.

I've only got about 300 hours logged but I have not once been asked WHY I am going around. However if you "intend" to do a touch-and-go or an abort/go around you must inform them, because it's their job to know where every aircraft is going. I usually tell the tower before takeoff I'll be flying a "closed pattern" if just practicing TnGs. Makes it much easier for ATC. When I intend to stop, I will say landing "Full Stop" when turning final. But, as Farhan said, if anything is off on approach or you bounce on touchdown, miss the touchdown zone, wind starts kicking your ass or if ANYTHING isn't perfect, it's full throttle, flaps up once +ROC, and figure out what u did wrong. The tower can wait, they are all in there watching, laughing at your pathetic attempt anyway. If something is wrong, do insist on priority access! POC is in charge after all. My alternator 172SP died on climbout once and I didn't say a thing, just rushed to mid field and dove vertical out of downwind pattern, slipping the hell out of it to slow her down. Per protocol, I didn't say a word to ATC until I was clear of the runway. But always be nice to the ATC. Fantastic guys that would do ANYTHING to keep their pilots safe. The FAA/NTSB tho.... they are the best reason to keep your mouth shut unless you are out of options!

I've got a few less hours than you and I've also never been asked why I've aborted my landing. I presume though that it's because there's generally been a healthy crosswind when I have. On an occasion where I was cleared for T&G and instead I came to a full stop (announced I would do that after I touched down when the landing felt like it could have been bad for my gear), the tower did ask why -- not that they were upset at my unscheduled change of plans, but to make sure there weren't any issues with the runway that would affect others.


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With similar weapons why does an AH64 Apache require a pilot and gunner when the A10 Warthog only needs a pilot?
The Apache has a 30mm chain gun. It carries Hellfire (anti armor), Stinger/Sidewinder (air to air) and Hydra (air to ground, APKWS guidance package available) missiles.

source
The Warthog has a 30mm gatling gun. It carries Maverick (30cm air to ground including armor), Hydra (70mm air to ground) and Sidewinder missiles, plus a variety of bombs.

source
The Warthog seems to have a more capable and complex weapons load, so why doesn't it use a separate gunner like the Apache?

From comments:
The ULB (Unmanned Little Bird) version of the AH6 can fly with two, one, or zero pilots, so it seems that helicopters can be automated like fixed wing aircraft.

source
The Kiowa Warrior 50cal machine gun was not turret mounted; it was fixed to the airframe like the A10, though not buried in it. This is used in an armed recon role, not attack.

source

One important fact is, helicopter is simpler harder to fly than airplane.

@user3528438 Simpler or harder?)

@Pilothead: I strongly suspect that's a typo (one of several), and it should read "...a helicopter is simply harder to fly than an airplane".

Mainly it's because the A10's pilot just has to point his aircraft at the target from a certain height while in forward flight, whereas the helicopter, being able to hover, needs to be able to engage a target while not pointed directly at it, while the pilot is busy flying a machine that takes a lot more attention than a fixed wing aircraft.
Especially when considering the Apache's original tactical function, which was to hover below the tree tops, pop up and engage a Soviet tank, and drop out of sight again.  As the pilot you wouldn't want to be managing the weapon systems AND flying the machine and avoiding obstacles.

Warthogs and Apaches are totally different animals. They're different types of vehicles, have different mission requirements and profiles, etc.
One possible explanation is that since the A-10's gun is fixed on the centerline of the aircraft, aiming it is essentially the same process as flying the jet, making the pilot most apt to handle the task. While it may be possible to design the variant of the A-10 with a separate crew station for a weapon systems officer etc., it probably is not needed for its air to mud role. The A-10 was designed around the single pilot role similar to what the A-1 Skyraider was during the Korean and Vietnam conflicts – a very simple and tough air-to-ground attack aircraft that carries largely unguided weapons and minimal avionics. Apaches largely make use of guided weapons, more sensors on board and more rolls to fulfill, so this may have justified the necessity for an additional gunner aboard.

I don’t know of any that were accepted into service.

One possibility is the AH-6 “Killer Egg” derivative of the MH-6 Little Bird.  They are military variants of the Hughes 500 D helicopter which was outfitted for ground attack against soft targets.

It should be stressed that helicopters have the gun always mounted on turret (with partial exception of Mi-24, where it can only be aimed up and down) and their pitch attitude basically never corresponds to their flight path (while for aircraft it always does except for few degrees).


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Is this a blisk?
GE Aviation bought the Czech company Walther to get their 600-800shp turboprop engines, now called the H75... On their website, two thirds down the page, the following picture has the caption

The H-series engines use blisks made from a single piece for the engine’s two axial compressor stages reduces component weight and part complexity

Is this a blisk?

100% not a blisk. I work with them on a daily bases. That is a disc with blades.

From Wikipedia's blisk:

A blisk (portmanteau of bladed disk) is a turbomachine component comprising both rotor disk and blades. It consists of a single part, instead of an assembly of a disk and individual, removable blades. Blisks may be additive manufactured, integrally cast, machined from a solid piece of material, or made by welding individual blades to a rotor disk. The term is used mainly in aerospace engine design. Blisks may also be known as integrally bladed rotors (IBR).

Figure 1. This device is clearly made up of many pieces.
I can't see how this could fit the Wikipedia definition so as far as they are concerned this is not a blisk.

Your cited definition says blisks may be "made by welding individual blades to a rotor disk.". You need to provide a source that shows these blades are removable, and not permanently fastened, now or at some later stage in the process.

@user71659: I don't think I need to do anything. Feel free to copy and improve.

@user71659 them blades are very clearly not welded. Once a blisk is welded and cleaned up you'd never know it wasn't once separate bits of metal. You also don't use the dovetail design for a welding blade's foot, you use it on removable blades.


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Does the Cessna 208B still require a part 23 waiver to operate with 14 seats?
The selected answer to this question refers to the applicability of part 23 to aircraft of nine passengers or less. Other countries certified the 208B with as many as fourteen passenger seats, using a waiver to allow the extra seats while relying on the FAA nine seat single engine certification base. The FAA normally required aircraft with ten to nineteen seats to be multi-engine.
The part 23 rewrite allows certification using ASTM standards, which provides for "level 4" occupancy of up to nineteen seats, and has a propulsion matrix with space for level 4 single engine aircraft. If the 208B were certified using the ASTM standards, would it still require a waiver to operate with more than nine passengers outside the US? Would it now be legal to operate this way inside the US under part 135?

I believe this is done under a supplemental type certificate.  And im pretty certain that the 14 passenger configuration is only applicable for skydiving operations.  (Where temporary "passengers" sit along the sides, either on a bench seat or on the floor)  If you ride in a Caravan you will quickly realize that there just isn't space for 14 conventional passenger seats.  If I was more confident I would make this an answer...

@MichaelHall This is the Grand Caravan which is bigger than the 208A model, but still I agree it is tight. The Cessna website shows the layout, four rows of 2+1 behind two crew seats.

yeah, I kinda used "Caravan" in the family context, to include both models.  (Which I have flown)  I actually did not know it entailed 2+1 rows, dang that must be tight!  And that's why I commented instead of answering...  Thanks for straightening me out.


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Is a wing lift distribution smooth in the presence of a prop?
Wings designed to minimize induced drag have a smooth distribution of lift from root to tip. Whether elliptical for span constrained wings or more bell shaped to minimize structural weight, ideal shapes do not have peaks and valleys.

However, when you take any shape and stick a prop in front of it, the distribution can change dramatically.

Do wing designers set lift distribution to be smooth before considering effects of the prop or after? Why?

It appears that at least in this case wings are designed without regard to propwash and the subsequent inefficiency is ignored or at least tolerated.

it also changes the lift distribution of the wing from the ideal elliptical distribution to a more rollercoaster value created by the propeller streams. The result is that a well-designed wing and tail get their carefully tailored lift distribution destroyed by propeller/rotor streams...wings thus have lower L/D than their designers believe in their basic lift/drag analysis.


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How does a forward lifting surface affect ideal lift distribution of a main wing?
In Peter K's answer to this elliptical wing with lowest drag question the minimum induced drag lift distribution for a wing is described as one with a constant downwash angle across its span. When a forward lifting surface is involved, as with a three surface aircraft, it creates its own downwash across its span and upwash beyond the tips. Both impinge on the larger main wing.
Is the combined minimum induced drag for both lifting surfaces still one where the main wing downwash angle is constant across its span?

@ymb1 That implies that the efficiency of the combined wing is evaluated in the same way as an isolated main wing, which would mean the answer to the above is yes.